Decorative elongated lamps are known wherein the installation of a conventional lamp control switch provides a means by which a series of lamp motions, such as the unified switching on/off, twinkling, or a quick/slow interval switching lamp on/off in a forward or reverse direction. In addition to these improvements, it achieved improvements in installation, transportation and application over conventional neon lights. Therefore, it is regarded as a product of excellent quality. However, the known lamp has only one main conducting wire having an appropriate number of strands wires and a supplementary conducting wire having an appropriate number of strands installed in the interior of the body of the conventional lamp, without the installation of a series wire. Therefore, the supplementary conducting wire has to be cut and used as a series wire. Its length is also made and set at a specific length to serve this purpose, making it impossible to be cut or shortened after the lamp has been fabricated. In addition, it is also found to be quite inconvenient when it is being installed.